The invention pertains to compounds that inhibit poly(ADP-ribose) polymerases, thereby retarding the repair of damaged DNA strands, and to methods of preparing such compounds. The invention also relates to the use of such compounds in pharmaceutical compositions and therapeutic treatments useful for potentiation of anti-cancer therapies, inhibition of neurotoxicity consequent to stroke, head trauma, and neurodegenerative diseases, and prevention of insulin-dependent diabetes.
Poly(ADP-ribose) polymerases (PARPs), nuclear enzymes found in almost all eukaryotic cells, catalyze the transfer of ADP-ribose units from nicotinamide adenine dinucleotide (NAD+) to nuclear acceptor proteins, and are responsible for the formation of protein-bound linear and branched homo-ADP-ribose polymers. Activation of PARP and resultant formation of poly(ADP-ribose) are induced by DNA strand breaks, e.g., after exposure to chemotherapy, ionizing radiation, oxygen free radicals, or nitric oxide (NO). The acceptor proteins of poly(ADP-ribose), including histones, topoisomerases, DNA and RNA polymerases, DNA ligases, and Ca2+- and Mg2+-dependent endonucleases, are involved in maintaining DNA integrity.
Because this cellular ADP-ribose transfer process is associated with the repair of DNA strand breakage in response to DNA damage caused by radiotherapy or chemotherapy, it can contribute to the resistance that often develops to various types of cancer therapies. Consequently, inhibition of PARP may retard intracellular DNA repair and enhance the antitumor effects of cancer therapy. Indeed, in vitro and in vivo data show that many PARP inhibitors potentiate the effects of ionizing radiation or cytotoxic drugs such as DNA methylating agents. Thus, inhibitors of the PARP enzyme are useful as adjunct cancer chemotherapeutics.
PARP inhibitors are additionally useful in therapy of cardiovascular diseases. Ischemia, a deficiency of oxygen and glucose in a part of the body, can be caused by an obstruction in the blood vessel supplying that area or a massive hemorrhage. Two severe forms, heart attack and stroke, are major killers in the developed world. Cell death results directly and also occurs when the deprived area is reperfused. PARP inhibitors are being developed to treat ischemia/reperfusion injuries. See, e.g., Zhang, xe2x80x9cPARP inhibition: a novel approach to treat ischemia/reperfusion and inflammation-related injuries,xe2x80x9d Emerging Drugs: The Prospect for Improved Medicines (1999), Ashley Publications Ltd. Inhibition of PARP has been shown to protect against myocardial ischemia and reperfusion injury (Zingarelli et al., xe2x80x9cProtection against myocardial ischemia and reperfusion injury by 3-aminobenzamide, an inhibitor of poly (ADP-ribose) synthetase,xe2x80x9d Cardiovascular Research (1997), 36:205-215).
Inhibitors of the PARP enzyme are also useful inhibitors of neurotoxicity consequent to stroke, head trauma, and neurodegenerative diseases. After brain ischemia, the distribution of cells with accumulation of poly(ADP-ribose), that is, the areas where PARP was activated, correspond to the regions of ischemic damage (Love et al., xe2x80x9cNeuronal accumulation of poly(ADP-ribose) after brain ischaemia,xe2x80x9d Neuropathology and Applied Neurobiology (1999), 25:98-103). It has been shown that inhibition of PARP promotes resistance to brain injury after stroke (Endres et al., xe2x80x9cIschemic Brain Injury is Mediated by the Activation of Poly(ADP-Ribose)Polymerase,xe2x80x9d J. Cerebral Blood Flow Metab. (1997), 17:1143-1151; Zhang, xe2x80x9cPARP Inhibition Results in Substantial Neuroprotection in Cerebral Ischemia,xe2x80x9d Cambridge Healthtech Institute""s Conference on Acute Neuronal Injury: New Therapeutic Opportunities, Sep. 18-24, 1998, Las Vegas, Nev.).
The activation of PARP by DNA damage is believed to play a role in the cell death consequent to head trauma and neurodegenerative diseases, as well as stroke. DNA is damaged by excessive amounts of NO produced when the NO synthase enzyme is activated as a result of a series of events initiated by the release of the neurotransmitter glutamate from depolarized nerve terminals (Cosi et al., xe2x80x9cPoly(ADP-Ribose) Polymerase Revisited: A New Role for an Old Enzyme: PARP Involvement in Neurodegeneration and PARP Inhibitors as Possible Neuroprotective Agents,xe2x80x9d Ann. N.Y. Acad. Sci. (1997), 825:366-379). Cell death is believed to occur as a result of energy depletion as NAD+ is consumed by the enzyme-catalyzed PARP reaction.
Parkinson""s disease is an example of a neurodegenerative condition whose progression may be prevented by PARP inhibition. Mandir et al. have demonstrated that mice that lack the gene for PARP are xe2x80x9cdramatically sparedxe2x80x9d from the effects of exposure to 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), a neurotoxin that causes parkinsonism in humans and animals (Mandir et al., xe2x80x9cPoly(ADP-ribose) polymerase activation mediates 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced parkinsonism,xe2x80x9d Proc. Natl. Acad. Sci. USA (1999), 96:5774-5779). MPTP potently activates PARP exclusively in dopamine-containing neurons of the substantia nigra, the part of the brain whose degeneration is associated with development of parkinsonism. Hence, potent PARP inhibitors may slow the onset and development of this crippling condition.
Furthermore, inhibition of PARP should be a useful approach for treatment of conditions or diseases associated with cellular senescence, such as skin aging, through the role of PARP in the signaling of DNA damage. See, e.g., U.S. Pat. No. 5,589,483.
PARP inhibition is also being studied at the clinical level to prevent development of insulin-dependent diabetes mellitus in susceptible individuals (Saldeen et al., xe2x80x9cNicotinamide-induced apoptosis in insulin producing cells in associated with cleavage of poly(ADP-ribose) polymerase,xe2x80x9d Mol. Cellular Endocrinol. (1998), 139:99-107). In models of Type I diabetes induced by toxins such as streptozocin and alloxan that destroy pancreatic islet cells, it has been shown that knock-out mice lacking PARP are resistant to cell destruction and diabetes development (Pieper et al., xe2x80x9cPoly (ADP-ribose) polymerase, nitric oxide, and cell death,xe2x80x9d Trends Pharmacolog. Sci. (1999), 20:171-181; Burkart et al., xe2x80x9cMice lacking the poly(ADP-ribose) polymerase gene are resistant to pancreatic beta-cell destruction and diabetes development induced by streptozocin,xe2x80x9d Nature Medicine (1999), 5:314-319). Administration of nicotinamide, a weak PARP inhibitor and a free-radical scavenger, prevents development of diabetes in a spontaneous autoimmune diabetes model, the non-obese, diabetic mouse (Pieper et al., ibid.). Hence, potent and specific PARP inhibitors may be useful as diabetes-prevention therapeutics.
PARP inhibition is also an approach for treating inflammatory conditions such as arthritis (Szabo et al., xe2x80x9cProtective effect of an inhibitor of poly(ADP-ribose) synthetase in collagen-induced arthritis,xe2x80x9d Portland Press Proc. (1998), 15:280-281; Szabo, xe2x80x9cRole of Poly(ADP-ribose) Synthetase in Inflammation,xe2x80x9d Eur. J. Biochem. (1998), 350(1):1-19; Szabo et al., xe2x80x9cProtection Against Peroxynitrite-induced Fibroblast Injury and Arthritis Development by Inhibition of Poly(ADP-ribose) Synthetase,xe2x80x9d Proc. Natl. Acad. Sci. USA (1998), 95(7):3867-72).
The PARP family of enzymes is extensive. It has recently been shown that tankyrases, which bind to the telomeric protein TRF-1, a negative regulator of telomere length maintenance, have a catalytic domain that is strikingly homologous to PARP and have been shown to have PARP activity in vitro. It has been proposed that telomere function in human cells is regulated by poly(ADP-ribosyl)ation. PARP inhibitors have utility as tools to study this function. Further, as a consequence of regulation of telomerase activity by tankyrase, PARP inhibitors should have utility as agents for regulation of cell life-span, e.g., for use in cancer therapy to shorten the life-span of tumor cells, or as anti-aging therapeutics, since telomere length is believed to be associated with cell senescence.
Various competitive inhibitors of PARP have been described. For example, Banasik et al. (xe2x80x9cSpecific Inhibitors of Poly(ADP-Ribose) Synthetase and Mono(ADP-Ribosyl)transferase,xe2x80x9d J. Biol. Chem. (1992) 267:1569-1575) examined the PARP-inhibiting activity of over one hundred compounds, the most potent of which were 4-amino-1,8-naphthalimide, 6(5H)-phenanthridone, 2-nitro-6(5H)-phenanthridone, and 1,5-dihydroxyisoquinoline. Griffin et al. reported the PARP-inhibiting activity for certain benzamide compounds (U.S. Pat. No. 5,756,510; see also xe2x80x9cNovel Potent Inhibitors of the DNA Repair Enzyme Poly(ADP-ribose)polymerase (PARP),xe2x80x9d Anti-Cancer Drug Design (1995), 10:507-514), benzimidazole compounds (International Publication No. WO 97/04771), and quinalozinone compounds (International Publication No. WO 98/33802). Suto et al. reported PARP inhibition by certain dihydroisoquinoline compounds (xe2x80x9cDihydroisoquinolines: The Design and Synthesis of a New Series of Potent Inhibitors of Poly(ADP-ribose) Polymerase,xe2x80x9d Anti-Cancer Drug Design (1991), 7:107-117). Griffin et al. have reported other PARP inhibitors of the quinazoline class (xe2x80x9cResistance-Modifying Agents. 5. Synthesis and Biological Properties of Quinazoline Inhibitors of the DNA Repair Enzyme Poly(ADP-ribose) Polymerase (PARP),xe2x80x9d J. Med. Chem. (1998) 41:5247-5256). International Publication Nos. WO 99/11622, WO 99/11623, WO 99/11624, WO 99/11628, WO 99/11644, WO 99/11645, and WO 99/11649 describe various PARP-inhibiting compounds. Furthermore, certain tricyclic PARP inhibitors are described in commonly owned U.S. Provisional Application No. 60/115,431, filed Jan. 11, 1999, in the name of Webber et al., the disclosure of which is incorporated by reference herein.
Nonetheless, there is still a need for small-molecule compounds that are active PARP inhibitors, especially those that have physical, chemical, and pharmacokinetic properties desirable for therapeutic applications.
Thus, an object of the invention is to discover small-molecule PARP-inhibiting compounds. Another object is to discover such compounds having properties advantageous for therapeutic uses.
The compounds of the general formula I have been discovered to be effective PARP inhibitors: 
wherein:
X is O or S;
Y is N or CR3, where R3 is: H;
halogen;
cyano;
an optionally substituted alkyl, alkenyl, alkynyl, cycloalkyl, heterocycloalkyl, aryl, or heteroaryl group (e.g., unsubstituted or substituted with one or more substituents selected from halogen, hydroxy, nitro, cyano, and amino, and alkoxy, alkyl, aryl, and heteroaryl groups unsubstituted or substituted with one or more substituents selected from halogen, hydroxy, nitro, cyano, and optionally substituted amino and ether groups (such as O-aryl)); or
xe2x80x94C(W)xe2x80x94R20, where W is O or S, and R20 is: H; OH; an optionally substituted alkyl, alkenyl, alkynyl, cycloalkyl, heterocycloalkyl, aryl, heteroaryl, O-alkyl, or O-aryl group (e.g., unsubstituted or substituted with one or more substituents selected from halogen, hydroxy, cyano, nitro, and amino, and alkyl and aryl groups unsubstituted or substituted with one or more substituents selected from halo, hydroxy, nitro, cyano, and amino); or NR27R28, where R27 and R28 are each independently H; OH; an optionally substituted alkyl, alkenyl, alkynyl, cycloalkyl, heterocycloalkyl, aryl, or heteroaryl group (e.g., unsubstituted or substituted with one or more substituents selected from alkyl, alkenyl, alkynyl, cycloalkyl, heterocycloalkyl, aryl, and heteroaryl groups unsubstituted or substituted with one or more substituents selected from halogen, hydroxy, nitro, cyano, amino, trifluoromethyl, alkyl and aryl groups);
xe2x80x94CR29xe2x95x90Nxe2x80x94R30, where R29 is H or an optionally substituted amino (e.g., dialkylamino), alkyl, alkenyl, alkynyl, cycloalkyl, heterocycloalkyl, aryl, heteroaryl, group. (e.g., unsubstituted or substituted with one or more substituents selected from halogen, hydroxy, cyano, nitro, and amino, and alkyl and aryl groups unsubstituted or substituted with one or more substituents selected from halogen, hydroxy, nitro, cyano, and amino), salkyl, sakyl, O-alkyl, or O-aryl and R30 is H, OH, an optionally substituted alkyl, alkenyl, alkynyl, cycloalkyl, heterocycloalkyl, aryl, heteroaryl, O-alkyl, or O-aryl group (e.g., unsubstituted or substituted with one or more substituents selected from halogen, hydroxy, cyano, nitro, and amino, and alkyl and aryl groups unsubstituted or substituted with one or more substituents selected from halogen, hydroxy, nitro, cyano, and amino), or NR31R32, where R31 and R32 are each independently H, OH, or an optionally substituted alkyl, alkenyl, alkynyl, cycloalkyl, heterocycloalkyl, aryl, or heteroaryl group (e.g., unsubstituted or substituted with one or more substituents selected from alkyl, alkenyl, alkynyl, cycloalkyl, heterocycloalkyl, aryl, and heteroaryl groups unsubstituted or substituted with one or more substituents selected from halogen, hydroxy, nitro, cyano, amino, trifluoromethyl, alkyl and aryl groups);
R1 is H;
halogen;
cyano;
an optionally substituted alkyl, alkenyl, alkynyl, cycloalkyl, heterocycloalkyl, aryl, or heteroaryl group (e.g., unsubstituted or substituted with one or more substituents selected from halogen, hydroxy, cyano, nitro, and amino, and alkyl, alkenyl, alkynyl, cycloalkyl, heterocycloalkyl, alkoxy, aryl, aryloxy, heteroaryl, and heteroaryloxy groups unsubstituted or substituted with one or more substituents selected from halogen, hydroxy, nitro, cyano, amino, lower alkoxy, trifluoromethyl, and alkylcarbonyl);
C(O)R12, where R12 is: H; an optionally substituted alkyl, alkenyl, alkynyl, cycloalkyl, heterocycloalkyl, aryl, or heteroaryl group (e.g., unsubstituted or substituted with one or more substituents selected from halogen, hydroxy, cyano, nitro, and amino, and alkyl and aryl groups unsubstituted or substituted with one or more substituents selected from halogen, hydroxy, nitro, cyano, and amino); or OR19 or NR21R22, where R19, R21 and R22 are each independently H or an optionally substituted alkyl, alkenyl, alkynyl, cycloalkyl, heterocycloalkyl, aryl, or heteroaryl group (e.g., unsubstituted or substituted with one or more substituents selected from alkyl, alkenyl, alkynyl, cycloalkyl, heterocycloalkyl, aryl, and heteroaryl groups unsubstituted or substituted with one or more substituents selected from halogen, hydroxy, nitro, cyano, amino, trifluoromethyl, alkyl and aryl groups);
OR13, where R13 is: H; an optionally substituted alkyl, alkenyl, alkynyl, cycloalkyl, heterocycloalkyl, aryl, or heteroaryl group (e.g., unsubstituted or substituted with one or more substituents selected from halogen, hydroxy, cyano, nitro, and amino, and alkyl and aryl groups unsubstituted or substituted with one or more substituents selected from halogen, hydroxy, nitro, cyano, and amino);
S(O)nNR16, where n is 0, 1 or 2, and R16 is: H; an optionally substituted alkyl, alkenyl, alkynyl, cycloalkyl, heterocycloalkyl, aryl, or heteroaryl group (e.g., unsubstituted or substituted with one or more substituents selected from halogen, hydroxy, cyano, nitro, and amino, and alkyl and aryl groups unsubstituted or substituted with one or more substituents selected from halogen, hydroxy, nitro, cyano, and amino); or NR23R24, where R23 and R24 are each independently H or an optionally substituted alkyl, alkenyl, alkynyl, cycloalkyl, heterocycloalkyl, aryl, or heteroaryl group (e.g., unsubstituted or substituted with one or more substituents selected from alkyl, alkenyl, alkynyl, cycloalkyl, heterocycloalkyl, aryl, and heteroaryl groups unsubstituted or substituted with one or more substituents selected from halogen, hydroxy, nitro, cyano, amino, trifluoromethyl, alkyl and aryl groups); or
NR17R18, where R17 and R18 are each independently: H; an optionally substituted alkyl, alkenyl, alkynyl, cycloalkyl, heterocycloalkyl, aryl, or heteroaryl group (e.g., unsubstituted or substituted with one or more substituents selected from alkyl, alkenyl, alkynyl, cycloalkyl, heterocycloalkyl, aryl, and heteroaryl groups unsubstituted or substituted with one or more substituents selected from halogen, hydroxy, nitro, cyano, amino, trifluoromethyl, alkyl and aryl groups); C(O)xe2x80x94R20 where R20 is: H, OH, an optionally substituted alkyl, alkenyl, alkynyl, cycloalkyl, heterocycloalkyl, aryl, heteroaryl, O-alkyl, or O-aryl group (e.g., unsubstituted or substituted with one or more substituents selected from halogen, hydroxy, cyano, nitro, and amino, and alkyl and aryl groups unsubstituted or substituted with one or more substituents selected from halo, hydroxy, nitro, cyano, and amino); or NR27R28, where R27 and R28 are each independently H; OH; an optionally substituted alkyl, alkenyl, alkynyl, cycloalkyl, heterocycloalkyl, aryl, or heteroaryl group (e.g., unsubstituted or substituted with one or more substituents selected from alkyl, alkenyl, alkynyl, cycloalkyl, heterocycloalkyl, aryl, and heteroaryl groups unsubstituted or substituted with one or more substituents selected from halogen, hydroxy, nitro, cyano, amino, trifluoromethyl, alkyl and aryl groups); or S(O)2NR25N26, where R25 and R26 are each independently H or an optionally substituted alkyl, alkenyl, alkynyl, cycloalkyl, heterocycloalkyl, aryl, or heteroaryl group (e.g., unsubstituted or substituted with one or more substituents selected from alkyl, alkenyl, alkynyl, cycloalkyl, heterocycloalkyl, aryl, and heteroaryl groups unsubstituted or substituted with one or more substituents selected from halogen, hydroxy, nitro, cyano, amino, trifluoromethyl, alkyl and aryl groups);
R2 is H or alkyl;
R4 is H, halogen or alkyl;
R5, R6, R7, and R8 are each independently selected from:
H;
an optionally substituted alkyl, alkenyl, alkynyl, cycloalkyl, heterocycloalkyl, aryl, or heteroaryl group (e.g., unsubstituted or substituted with one or more substituents selected from halogen, hydroxy, nitro, and amino, and alkoxy, alkyl, and aryl groups unsubstituted or substituted with one or more substituents selected from halogen, hydroxy, nitro, cyano, and optionally substituted amino and ether groups (such as O-aryl)); and
xe2x80x94C(O)xe2x80x94R50, where R50 is: H; an optionally substituted alkyl, alkenyl, alkynyl, cycloalkyl, heterocycloalkyl, aryl, or heteroaryl group (e.g., unsubstituted or substituted with one or more substituents selected from halogen, hydroxy, nitro, and amino, and alkyl and aryl groups unsubstituted or substituted with one or more substituents selected from halogen, hydroxy, nitro, and amino); or OR51 or NR52R53, where R51, R52 and R53 are each independently H or an optionally substituted alkyl, alkenyl, alkynyl, cycloalkyl, heterocycloalkyl, aryl, or heteroaryl group (e.g., unsubstituted or substituted with one or more substituents selected from alkyl, alkenyl, alkynyl, cycloalkyl, heterocycloalkyl, aryl, and heteroaryl groups unsubstituted or substituted with one or more substituents selected from halogen, hydroxy, nitro, and amino, and alkyl and aryl groups unsubstituted or substituted with one or more substituents selected from halogen, hydroxy, nitro, and optionally substituted amino groups);
where when Y is CR3, R1, R2, R3, R4, R5, R6, R7, and R8 are not all H.
The invention is also directed to pharmaceutically acceptable salts, prodrugs, active metabolites, and solvates of compounds of formula I.
Preferably, the compounds of formula I have a PARP-inhibiting activity corresponding to a Ki of 10 xcexcM or less in the PARP enzyme inhibition assay.
The present invention is also directed to pharmaceutical compositions each comprising an effective PARP-inhibiting amount of an agent selected from compounds of formula I and their pharmaceutically acceptable salts, prodrugs, active metabolites, and solvates, in combination with a pharmaceutically acceptable carrier therefor.
The present invention is also directed to a method of inhibiting PARP enzyme activity, comprising contacting the enzyme with an effective amount of a compound of formula I or a pharmaceutically acceptable salt, prodrug, active metabolite, or solvate thereof. The invention is also directed to therapeutic methods comprising inhibiting ARP enzyme activity in the relevant tissue of a patient by administering a compound of formula I or a pharmaceutically acceptable salt, prodrug, active metabolite, or solvate thereof.
Other embodiments, objects and advantages of the invention will become apparent from the following detailed description.
In accordance with a convention used in the art, the symbol 
is used in structural formulas herein to depict the bond that is the point of attachment of the moiety or substituent to the core or backbone structure. In accordance with another convention, in some structural formulae herein the carbon atoms and their bound hydrogen atoms are not explicitly depicted, e.g., 
represents a methyl group, 
represents an ethyl group, 
represents a cyclopentyl group, etc.
As used herein, the term xe2x80x9calkylxe2x80x9d means a branched- or straight-chained (linear) paraffinic hydrocarbon group (saturated aliphatic group) having from 1 to 16 carbon atoms in its chain, which may be generally represented by the formula CkH2k+1, where k is an integer of from 1 to 10. Examples of alkyl groups include methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, t-butyl, pentyl, n-pentyl, isopentyl, neopentyl, and hexyl, and the simple aliphatic isomers thereof. A xe2x80x9clower alkylxe2x80x9d is intended to mean an alkyl group having from 1 to 4 carbon atoms in its chain.
The term xe2x80x9calkenylxe2x80x9d means a branched- or straight-chained olefinic hydrocarbon group (unsaturated aliphatic group having one or more double bonds) containing 2 to 10 carbons in its chain. Exemplary alkenyls include ethenyl, 1-propenyl, 2-propenyl, 1-butenyl, 2-butenyl, isobutenyl, and the various isomeric pentenyls and hexenyls (including both cis and trans isomers).
The term xe2x80x9calkynylxe2x80x9d means a branched or straight-chained hydrocarbon group having one or more carbon-carbon triple bonds and from 2 to 10 carbon atoms in its chain. Exemplary alkynyls include ethynyl, propynyl, 1-butynyl, 2-butynyl, and 1-methyl-2-butynyl.
The term xe2x80x9ccarbocyclexe2x80x9d refers to a saturated, partially saturated, unsaturated, or aromatic, monocyclic or fused or non-fused polycyclic, ring structure having only carbon ring atoms (no heteroatoms, i.e., non-carbon ring atoms). Exemplary carbocycles include cycloalkyl, aryl, and cycloalkyl-aryl groups.
The term xe2x80x9cheterocyclexe2x80x9d refers to a saturated, partially saturated, unsaturated, or aromatic, monocyclic or fused or non-fused polycyclic, ring structure having one or more heteroatoms selected from nitrogen, oxygen and sulfur. Exemplary heterocycles include heterocycloalkyl, heteroaryl, and heterocycloalkyl-heteroaryl groups.
A xe2x80x9ccycloalkyl groupxe2x80x9d is intended to mean a non-aromatic monovalent, monocyclic or fused polycyclic, ring structure having a total of from 3 to 18 carbon ring atoms (but no heteroatoms). Exemplary cycloalkyls include cyclopropyl, cyclobutyl, cyclopentyl, cyclopentenyl, cyclohexyl, cycloheptyl, adamantyl, phenanthrenyl, and like groups.
A xe2x80x9cheterocycloalkyl groupxe2x80x9d is intended to mean a non-aromatic monovalent, monocyclic or fused polycyclic, ring structure having a total of from 3 to 18 ring atoms, including 1 to 5 heteroatoms selected from nitrogen, oxygen, and sulfur. Illustrative examples of heterocycloalkyl groups include pyrrolidinyl, tetrahydrofuryl, piperidinyl, piperazinyl, morpholinyl, thiomorpholinyl, aziridinyl, and like groups.
The term xe2x80x9carylxe2x80x9d means an aromatic monocyclic or fused polycyclic ring structure having a total of from 4 to 18 ring carbon atoms (no heteroatoms). Exemplary aryl groups include phenyl, naphthyl, anthracenyl, and the like.
A xe2x80x9cheteroaryl groupxe2x80x9d is intended to mean an aromatic monovalent, monocyclic or fused polycyclic, ring structure having from 4 to 18 ring atoms, including from 1 to 5 heteroatoms selected from nitrogen, oxygen, and sulfur. Illustrative examples of heteroaryl groups include pyrrolyl, thienyl, oxazolyl, pyrazolyl, thiazolyl, furyl, pyridinyl, pyrazinyl, triazolyl, tetrazolyl, indolyl, quinolinyl, quinoxalinyl, and the like.
An xe2x80x9caminexe2x80x9d or xe2x80x9camino groupxe2x80x9d is intended to mean the radical xe2x80x94NH2, and xe2x80x9coptionally substitutedxe2x80x9d amines refers to xe2x80x94NH2 groups wherein none, one or two of the hydrogens is replaced by a suitable substituent. Disubstituted amines may have substituents that are bridging, i.e., form a heterocyclic ring structure that includes the amine nitrogen. An xe2x80x9calkylamino groupxe2x80x9d is intended to mean the radical xe2x80x94NHRa, where Ra is an alkyl group. A xe2x80x9cdialkylamino groupxe2x80x9d is intended to mean the radical xe2x80x94NRaRb, where Ra and Rb are each independently an alkyl group.
The term xe2x80x9coptionally substitutedxe2x80x9d is intended to indicate that the specified group is unsubstituted or substituted by one or more suitable substituents, unless the optional substituents are expressly specified, in which case the term indicates that the group is unsubstituted or substituted with the specified substituents. Unless indicated otherwise (e.g., by indicating that a specified group is unsubstituted), the various groups defined above may be generally unsubstituted or substituted (i.e., they are optionally substituted) with one or more suitable substituents.
The term xe2x80x9csubstituentxe2x80x9d or xe2x80x9csuitable substituentxe2x80x9d is intended to mean any substituent for a group that may be recognized or readily selected by the artisan, such as through routine testing, as being pharmaceutically suitable. Illustrative examples of suitable substituents include hydroxy, halogen (F, Cl, I, or Br), oxo, alkyl, acyl, sulfonyl, mercapto, nitro, alkylthio, alkoxy, cycloalkyl, heterocycloalkyl, aryl, heteroaryl, carboxy, amino (primary, secondary, or tertiary), carbamoyl, aryloxy, heteroaryloxy, arylthio, heteroarylthio, and the like (e.g., as illustrated by the exemplary compounds described herein).
Preferred optional substituents for alkyl and aryl groups in the compounds of the invention include halogens and aryl groups. Substituted alkyl groups include perfluoro-substituted alkyls, and optional substituents for alkyl and aryl moieties include halogen; lower alkyl optionally substituted by xe2x80x94OH, xe2x80x94NH2, or halogen; xe2x80x94OH; xe2x80x94NO2; xe2x80x94CN; xe2x80x94CO2H; O-lower alkyl; aryl; xe2x80x94O-aryl; aryl-lower alkyl; xe2x80x94OCHF2; xe2x80x94CF3; xe2x80x94OCF3; xe2x80x94CO2Ra, xe2x80x94CONRaRb, xe2x80x94OCH2CONRaRb, xe2x80x94NRaRb, xe2x80x94SO2RaRb, where Ra and Rb are each independently H, lower alkyl, or aryl; and the like. Aryl moieties may also be optionally substituted by two substituents forming a bridge, for example xe2x80x94Oxe2x80x94(CH2)zxe2x80x94Oxe2x80x94, where z is an integer of 1, 2, or 3.
A xe2x80x9cprodrugxe2x80x9d is intended to mean a compound that is converted under physiological conditions or by solvolysis, or metabolically, to a specified compound that is pharmaceutically active.
An xe2x80x9cactive metabolitexe2x80x9d is intended to mean a pharmacologically active product produced through metabolism in the body of a specified compound. Metabolic products of a given compound may be identified using techniques generally known in the art for determining metabolites and assaying them for their activity using techniques such as those described below.
Prodrugs and active metabolites of a compound may be identified using routine techniques known in the art. See, e.g., Bertolini, G. et al., J. Med. Chem., 40, 2011-2016 (1997); Shan, D. et al., J. Pharm. Sci., 86 (7), 765-767; Bagshawe K., Drug Dev. Res., 34, 220-230 (1995); Bodor, N., Advances in Drug Res., 13, 224-331 (1984); Bundgaard, H., Design of Prodrugs (Elsevier Press 1985); and Larsen, I. K., Design and Application of Prodrugs, Drug Design and Development (Krogsgaard-Larsen et al., eds., Harwood Academic Publishers, 1991).
A xe2x80x9csolvatexe2x80x9d is intended to mean a pharmaceutically acceptable solvate form of a specified compound that retains the biological effectiveness of such compound. Examples of solvates include compounds of the invention in combination with water, isopropanol, ethanol, methanol, DMSO, ethyl acetate, acetic acid, or ethanolamine.
A xe2x80x9cpharmaceutically acceptable saltxe2x80x9d is intended to mean a salt that retains the biological effectiveness of the free-acid or base form of the specified compound and that is pharmaceutically suitable. Examples of pharmaceutically acceptable salts include sulfates, pyrosulfates, bisulfates, sulfites, bisulfites, phosphates, monohydrogenphosphates, dihydrogenphosphates, metaphosphates, pyrophosphates, chlorides, bromides, iodides, acetates, propionates, decanoates, caprylates, acrylates, formates, isobutyrates, caproates, heptanoates, propiolates, oxalates, malonates, succinates, suberates, sebacates, fumarates, maleates, butyne-1,4-dioates, hexyne-1,6-dioates, benzoates, chlorobenzoates, methylbenzoates, dinitrobenzoates, hydroxybenzoates, methoxybenzoates, phthalates, sulfonates, xylenesulfonates, phenylacetates, phenylpropionates, phenylbutyrates, citrates, lactates, xcex3-hydroxybutyrates, glycollates, tartrates, methancsulfonates, propanesulfonates, naphthalene-1-sulfonates, naphthalene-2-sulfonates, and mandelates.
If an inventive compound is a base, a desired salt may be prepared by any suitable method known in the art, including treatment of the free base with: an inorganic acid, such as hydrochloric acid, hydrobromic acid, sulfuric acid, nitric acid, phosphoric acid, and the like; or with an organic acid, such as acetic acid, maleic acid, succinic acid, mandelic acid, fumaric acid, malonic acid, pyruvic acid, oxalic acid, glycolic acid, salicylic acid, pyranosidyl acid such as glucuronic acid or galacturonic acid; alpha-hydroxy acid such as citric acid or tartaric acid; amino acid such as aspartic acid or glutamic acid; aromatic acid such as benzoic acid or cinnamic acid; sulfonic acid such as p-toluenesulfonic acid or ethanesulfonic acid; or the like.
If an inventive compound is an acid, a desired salt may be prepared by any suitable method known in the art, including treatment of the free acid with an inorganic or organic base, such as an amine (primary, secondary, or tertiary), an alkali metal or alkaline earth metal hydroxide, or the like. Illustrative examples of suitable salts include: organic salts derived from amino acids such as glycine and arginine; ammonia; primary, secondary, and tertiary amines; and cyclic amines, such as piperidine, morpholine, and piperazine; as well as inorganic salts derived from sodium, calcium, potassium, magnesium, manganese, iron, copper, zinc, aluminum, and lithium.
In the case of compounds, salts, or solvates that are solids, it is understood by those skilled in the art that the inventive compounds, salts, and solvates may exist in different crystalline or polymorph forms, all of which are intended to be within the scope of the present invention and specified formulas.
In some cases, the inventive compounds will have chiral centers. When chiral centers are present, the inventive compounds may exist as single stereoisomers, racemates, and/or mixtures of enantiomers and/or diastereomers. All such single stereoisomers, racemates, and mixtures thereof are intended to be within the broad scope of the generic structural formulae (unless otherwise indicated). Preferably, however, the inventive compounds are used in essentially optically pure form (as generally understood by those skilled in the art, an optically pure compound is one that is enantiomerically pure). Preferably, the compounds of the invention are at least 90% of the desired single isomer (80% enantiomeric excess), more preferably at least 95% (90% e.e.), even more preferably at least 97.5% (95% e.e.), and most preferably at least 99% (98% e.e.).
The tautomeric forms of the compounds of formula I are also intended to be covered by the depicted general formula. For example, when R1 is OH or SH and Y is N, the tautomeric forms of formula I are available.
Preferred R1 groups for compounds of formula I include unsubstituted, mono- and di-substituted aryl and heteroaryl groups; and alkyl groups unsubstituted or substituted with optionally substituted aryl or heteroaryl groups. Also preferred are compounds wherein R1 is: C(O)R12, where R12 is alkyl or NR21, R22; or S(O)nR16, where R16 is H or alkyl and n is 0, 1, or 2 (the sulfur atom is partially or fully oxidized). R2 is preferably H or lower alkyl. R4 is preferably H or halogen. R5, R6, R7, and R8 are each preferably H or an optionally substituted alkyl or acyl group.
In other preferred embodiments of the formula I, R1 is optionally substituted aryl or heteroaryl; R2 is H; R4 is H or halogen; R5, R6, R7, and R8 are each H; and X is oxygen.
In other preferred embodiments of formula I, R1 is OH or SH, and Y is N. More preferably, such compounds are the tautomers of formula I represented by formula II, where Z is O or S, R9 is H or alkyl, and all other variables have the definitions given above: 
In preferred embodiments of formula II, R2 and R9 are each independently H or methyl, R4 is H or halogen, R5, R6, R7, and R8 are each H, and X is oxygen.
In further preferred embodiments, the PARP-inhibiting compounds are represented by formula III: 
wherein:
Y is as defined above;
R11 is an aryl or heteroaryl group unsubstituted or substituted with one or more substituents selected from halogen, hydroxy, nitro, and amino, and alkyl, aryl, heteroaryl, alkoxy, aryloxy, and heteroaryloxy groups unsubstituted or substituted with one or more substituents selected from halogen, hydroxy, lower alkoxy, cyano, nitro, and amino; and
R14 is H or halogen.
In preferred embodiments of formula III, R11 is mono- or di-substituted phenyl.
Preferred species of the invention include: 
Especially preferred species are described in the Examples as Examples 2, 6, 8, 14, 34, 37, 58, 59, 75, 82, 98, 99, 119, 129, 130, 132, 134, 137, 141, 142, 148, 149, 170, 171, 177, 184, 186, 197, 203, 207, 210, 211, 212, 223, 233, 245 and 246.
The invention is also directed to a method of inhibiting PARP enzyme activity, comprising contacting the enzyme with an effective amount of a compound of formula I, II, or III, or a pharmaceutically acceptable salt, prodrug, active metabolite, or solvate thereof (collectively, xe2x80x9cagentsxe2x80x9d). For example, PARP activity may be inhibited in mammalian tissue by administering such an agent.
xe2x80x9cTreatingxe2x80x9d or xe2x80x9ctreatmentxe2x80x9d is intended to mean mitigating or alleviating an injury is or a disease condition in a mammal, such as a human, that is mediated by the inhibition of PARP activity, such as by potentiation of anti-cancer therapies or inhibition of neurotoxicity consequent to stroke, head trauma, and neurodegenerative diseases. Types of treatment include: (a) as a prophylactic use in a mammal, particularly when the mammal is found to be predisposed to having the disease condition but not yet diagnosed as having it; (b) inhibition of the disease condition; and/or (c) alleviation, in whole or in part, of the disease condition.
The invention also provides therapeutic interventions appropriate in disease or injury states where PARP activity is deleterious to a patient. For example, the tricyclic compounds of the invention are useful for treating cancer, inflammation, the effects of heart attack, stroke, head trauma and neurodegenerative disease, and diabetes.
One treatment method involves improving the effectiveness of a cytotoxic drug and/or radiotherapy administered to a mammal in the course of therapeutic treatment, comprising administering to the mammal an effective amount of a PARP-inhibiting agent (compound, pharmaceutically acceptable salt, prodrug, active metabolite, or solvate) in conjunction with administration of the cytotoxic drug (e.g., topotecan, irinotecan, temozolimide) and/or radiotherapy. The agents of the invention preferably have a cytotoxicity potentiation activity corresponding to a PF50 of greater than I in the cytotoxicity potentiation assay.
The PARP-inhibiting agents may also be advantageously used in a method for reducing neurotoxicity consequent to stroke, head trauma, and neurodegenerative diseases in a mammal by administering a therapeutically effective amount of an inventive agent to the mammal.
The PARP-inhibiting agents of the invention may also be used in a method for delaying the onset of cell senescence associated with skin aging in a human, comprising administering to fibroblast cells in the human an effective PARP-inhibiting amount of an agent.
Further, the agents may also be used in a method for helping prevent the development of insulin-dependent diabetes mellitus in a susceptible individual, comprising administering a therapeutically effective amount of an agent.
Additionally, the agents may also be employed in a method for treating an inflammatory condition in a mammal, comprising administering a therapeutically effective amount of an agent to the mammal.
Moreover, the agents may also be used in a method for treating cardiovascular disease in a mammal, comprising administering to the mammal a therapeutically effective amount of a PARP-inhibiting agent. More particularly, a therapeutic intervention method provided by the present invention is a cardiovascular therapeutic method for protecting against myocardial ischemia and reperfusion injury in a mammal, comprising administering to the mammal an effective amount of a compound of formula I, II, or III or a pharmaceutically acceptable salt, prodrug, active metabolite, or solvate thereof.
The activity of the inventive agents as inhibitors of PARP activity may be measured by any of the suitable methods known or available in the art, including by in vivo and in vitro assays. An example of a suitable assay for activity measurements is the PARP enzyme inhibition assay described herein.
Administration of the compounds of the formula I, II, or III and their pharmaceutically acceptable prodrugs, salts, active metabolites, and solvates may be performed according to any of the generally accepted modes of administration available in the art. Illustrative examples of suitable modes of administration include intravenous, oral, nasal, parenteral, topical, transdermal, and rectal delivery. Oral and intravenous delivery are preferred.
An inventive agent may be administered as a pharmaceutical composition in any pharmaceutical form recognizable to the skilled artisan as being suitable. Suitable pharmaceutical forms include solid, semisolid, liquid, or lyophilized formulations, such as tablets, powders, capsules, suppositories, suspensions, liposomes, and aerosols. Pharmaceutical compositions of the invention may also include suitable excipients, diluents, vehicles, and carriers, as well as other pharmaceutically active agents (including other PARP-inhibiting agents), depending upon the intended use.
Acceptable methods of preparing suitable pharmaceutical forms of the compositions are generally known or may be routinely determined by those skilled in the art. For example, pharmaceutical preparations may be prepared following conventional techniques of the pharmaceutical chemist involving steps such as mixing, granulating, and compressing when necessary for tablet forms, or mixing, filling, and dissolving the ingredients as appropriate to give the desired products for intravenous, oral, parenteral, topical, intravaginal, intranasal, intrabronchial, intraocular, intraaural, and/or rectal administration.
Solid or liquid pharmaceutically acceptable carriers, diluents, vehicles, or excipients may be employed in the pharmaceutical compositions. Illustrative solid carriers include starch, lactose, calcium sulphate dihydrate, terra alba, sucrose, talc, gelatin, pectin, acacia, magnesium stearate, and stearic acid. Illustrative liquid carriers include syrup, peanut oil, olive oil, saline solution, and water. The carrier or diluent may include a suitable prolonged-release material, such as glyceryl monostearate or glyceryl distearate, alone or with a wax. When a liquid carrier is used, the preparation may be in the form of a syrup, elixir, emulsion, soft gelatin capsule, sterile injectable liquid (e.g., solution), or a nonaqueous or aqueous liquid suspension.
A dose of the pharmaceutical composition contains at least a therapeutically effective amount of a PARP-inhibiting agent (i.e., a compound of formula I, II, or III, or a pharmaceutically acceptable salt, prodrug, active metabolite, or solvate thereof), and preferably contains one or more pharmaceutical dosage units. The selected dose may be administered to a mammal, for example, a human patient, in need of treatment of a condition mediated by inhibition of PARP activity, by any known or suitable method of administering the dose, including: topically, for example, as an ointment or cream; orally; rectally, for example, as a suppository; parenterally by injection; or continuously by intravaginal, intranasal, intrabronchial, intraaural, or intraocular infusion. A xe2x80x9ctherapeutically effective amountxe2x80x9d is intended to mean the amount of an agent that, when administered to a mammal in need thereof, is sufficient to effect treatment for injury or disease condition mediated by inhibition of PARP activity. The amount of a given agent of the invention that will be therapeutically effective will vary depending upon factors such as the particular agent, the disease condition and the severity thereof, the identity of the mammal in need thereof, which amount may be routinely determined by artisans.
It will be appreciated that the actual dosages of the PARP-inhibiting agents used in the pharmaceutical compositions of this invention will be selected according to the properties of the particular agent being used, the particular composition formulated, the mode of administration and the particular site, and the host and condition being treated. Optimal dosages for a given set of conditions can be ascertained by those skilled in the art using conventional dosage-determination tests. For oral administration, e.g., a dose that may be employed is from about 0.001 to about 1000 mg/kg body weight, with courses of treatment repeated at appropriate intervals.
The PARP-inhibiting agents of the invention may be synthesized according to the processes described below, such as the one of the following general processes. 
In this process, an ortho-substituted-aniline (Ia) is alkylated to an N-substituted intermediate (IIa), which can be further converted to cyclic ketone (IIIa). The ketone (IIIa) can be transformed to a compound of formula I via alternative routes. When Q is a nitro group, it can be reduced to the corresponding amine and further used in a reaction with an acid chloride to provide tricyclic ketone intermediate (IVa). Ring expansion of (IVa) yields a tricyclic amide with formula I (Y=N, X=O), which may be further derivatized. A more preferred and alternative route for the conversion of a ketone (IIIa) to I (Y=N) or II (Z=O, S) involves first performing the ring expansion step to yield intermediate amide (Va), followed by reduction of the nitro group and cyclization with an acid chloride, aldehyde, or any reagent used to form a urea or thiourea. The product formed may also be further derivatized. For intermediate (IIIa) when Q is an appropriate leaving group, however, it can be transformed to an acetylene derivative (Va) where Q is Cxe2x89xa1Cxe2x80x94R1, which is further converted to I (Y=CH). The product formed may also be further derivatized. 
Under this reaction scheme, an indoline (Ib) is alkylated to the N-substituted intermediate (IIb), which is further converted to tricyclic ketone (IIIb). The tricyclic ketone (IIIb) is exposed to conditions for ring expansion and oxidized to yield compounds of formula I (Y=CH), which may be further derivatized. 
In this process, a nitro-anthranilic acid (Ic) or nitro-isotoic anhydride (IIc) is transformed to an intermediate amino acylbenzamide (IIIc). This intermediate is further transformed to the ortho-nitro cyclic imine (IVc). The imine and nitro functionalities are concomitantly reduced followed by cyclization with an acid chloride, aldehyde, or reagent used to form a urea or thiourea yielding compounds of formula I (Y=N) or II (Z=O, S). 
Compounds of formula I (Y=N) or II (Z=O, S) can also be prepared via an alternative route from intermediate Va (Q=NO2). Nitro-anthranilic acid (Ic) is first converted to nitro-benzoic acid ester (Id), where X is a halide or an appropriate leaving group, followed by cyclization to Va with an appropriate ethylenediamine.
More particularly, the following reaction schemes are useful in the preparation of the illustrated compounds of the invention. 
In this scheme, 2-nitroaniline A (R40=H, F) is N-alkylated with acrylonitrile to yield B. The nitrile group of B is hydrolyzed to carboxylic acid C, which is subjected to Friedel-Craft-type intramolecular cyclization conditions to form ketone D. Nitro-ketone D is reduced to the diamino-ketone G, which undergoes cyclization to H (R1=aryl, alkyl) when exposed to an acid chloride or aldehyde. Tricyclic ketone H can be transformed via a Schmidt-type reaction with NaN3 and acid to tricyclic lactam I. Alternatively and preferable, nitro-ketone D is first transformed to tricylic lactam E via the Schmidt reaction, reduced to diamino-lactam F, and further exposed to an acid chloride, aldehyde, CS2, thiophosgene, thiocarbonyl diimidazole or equivalent reagent to form I (R1=aryl, alkyl, SH). Diamino-lactam F may also be converted to tricyclic lactam J when exposed to phosgene, carbonyl diimidazole or equivalent reagent. In all cases, I may be optionally modified at R1. 
In this scheme, 3-nitroanthranilic acid Z (R40=H) is converted to methyl ester FF (R40=H). Diazotization of the amino group of FF (R40=H) and halogenation transforms it into bromide GG (R40=H). The cyclic lactam E (R40=H) is formed by displacement of the bromide and subsequent cyclization with ethylene diamine. 
Here, 2-iodoaniline K is N-alkylated with xcex2-propiolactone to yield L, which is subjected to Friedel-Craft-type intramolecular cyclization conditions to form ketone M. Iodo-ketone M is transformed to iodo-lactam N via a Schmidt-type reaction with NaN3 and acid. Intermediate N is converted to the corresponding substituted acetylene O, is where R1 is aryl, alkyl, H or xe2x80x94Si(alkyl)3, using a metal-catalyzed reaction, typically employing both palladium and copper(I). Tricyclic lactam P is formed by further exposing acetylene O to a metal-catalyzed reaction, typically using palladium. P is optionally modified at R1 and R10. 
In this scheme, indoline Q is N-alkylated with acrylonitrile to yield R. The nitrile group of R is hydrolyzed to carboxylic acid S, which is subjected to Friedel-Craft-type intramolecular cyclization conditions to form ketone T. Tricyclic ketone T is exposed to Schmidt-type ring-expansion reaction conditions with NaN3 and acid to form tricyclic lactam U. Intermediate U is oxidized to produce V, which can then be further modified. For example, V can be halogenated or formylated to W, where R10=I, CHO. In all cases W is optionally modified at R10. Product W may also be halogenated to product X, where the formula variable X is iodine. Product X can be transformed via a metal-catalyzed reaction (typically with palladium as catalyst) into a number of different tricyclic lactams P where R1 is aryl, etc. P may be optionally modified at R1 and R10. 
In this scheme, 3-nitroanthranilic acid Z (R40=H) is converted sequentially to intermediate amide AA and cyclic imine BB, which are usually not isolated, but further subjected to hydrogenation to form cyclic diamino-lactam CC where R7 or R8 is H, alkyl, or aryl. When CC (one of R7 and R8 must be H) is further exposed to an acid chloride, aldehyde, CS2, thiophosgene, thiocarbonyl diimidazole or equivalent reagent, tricyclic lactam DD is formed (R1=aryl, alkyl, SH; R7 or R8=H, alkyl, or aryl.). Diamino-lactam CC may also be converted to tricyclic lactam EE when exposed to phosgene, carbonyl diimidazole or equivalent reagent. In all cases DD and EE are optionally modified at R1, R7, and/or R8.